Contracts for Ames Salmonella assay support and Mouse Lymphoma assay support are required by the Office of the Director, DCE for its support of extramural and intramural activities of the Division. The primary thrust has been to support the NCI selection process for carcinogenicity testing in the National Toxicology Program (NTP). The NCI, and specifically DCE, plays a major role in nominating chemical candidates for carcinogenicity testing by the NTP, a responsibility the NCI retained when the bioassay program developed by this Division was transferred to the NTP in 1978. This Division has evolved a format to look at large groupings of chemicals (by structure or use category) to systematically select the best candidates. This has routinely shown that there is a paucity of in vitro data on most of the compounds, and of our 75 nominations over the last five years, 50 were tested in these two assays to supply the necessary information. Data obtained from the existing in vitro contracts has thus permitted our selection group to make more informed choices in a timely fashion.